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Man-Powered Flashlight Help Answered

For anyone good with electronics and motors,

I'm tasked with building a flashlight powered by man and I'm in need of assistance. I've decided to make it crank powered. Now what I really need help with is this- Can I make a crank that powers an electric motor that charges a battery to power the LED lights? What would be the best way to go about this?


Buy a cheap hand-cranked flashlight, I bought a hand-cranked radio/flashlight for 7 bucks at Tractor Supply. Here is a pic.


Or you could just take an old printer some of them have spesial motors inside they are called phase motors they can generate a lot of power with just a little turn. pleaz reply

That would be great and all, but I have no spare printer laying around.

Go to the local dump and find one ! For an engineer, you are signally lacking in imagination.

Have a look at an old cordless drills, they are free or cheap, have a gearbox and motor, plus its easy to fit a crank into the chuck. Just remove the trigger and wire your LEDS to the motor. Or you could find a big stepper motor and not have a gearbox at all. Have a look at this (The link tool seem to be broken?)




I just looked at it, thank you. It will definitely give me some insight to what I'll end up doing later. Once I go into class tomorrow, I'm going to see what scrap motors we have because I don't have anything around that I can sacrifice.

It's all about the gearing between the crank and the motor. You'll want one turn of the crank to produce multiple turns on the motor.

I suggest taking a less complicated rout and build a light powered from shaking it like this instructable.

Alright, so what would be a ballpark figure, a good ratio of turns of the crank to turns on the motor that would make it fairly efficient? I've looked at the shake lights and for what I'm doing, a crank system is better because it holds more power for a longer duration.

Be it crank or shake the systems charges a battery. Your choice in batteries decides how long it lasts.

As for gear ratio that depends on the motor you use. It's a balancing act really. Since you want an average crank speed to spin the motor at it's average RPM to generate power. But at the same time the more turns you produce from your single turn of the crank means you have to put more force into the crank. Meaning more stress on the gears and risk of stripping the gears. I suggest getting a cheap crank light and basing your design off it. There are cheap key chain crank lights.

Fair enough then, this is all for a project in my intro engineering class and we're all going in dark on this project. When I go back into the class Monday I'll have to see what components we have. I think I'll end up using a 9V battery and a small DC motor. Thanks, you've been helpful.

Bear in mind that the only way to get 9V out of 9V motor is to spin it at the same speed it runs at as a motor. If it runs at 10,000 RPM on 9V....you have to turn it at 10,000RPM to get 9V out. And that's off load.

I'm not trying to buy one, I actually have to make one as part of an engineering project.

Since you clearly know very little about the task, buying one, studying it, replicating it, then improving it, seems like a plan to me.

Exactly! Everything in engineering and science is built off the work done by those who came before us. You gotta base your design off something so i see no reason you couldn't use an existing product as research material. Than you can make your own adjustments to the design and create something new.